From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0FE92C64E7D for ; Sun, 29 Nov 2020 12:27:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CABA120829 for ; Sun, 29 Nov 2020 12:27:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="tLLVBytJ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726986AbgK2M0z (ORCPT ); Sun, 29 Nov 2020 07:26:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725830AbgK2M0y (ORCPT ); Sun, 29 Nov 2020 07:26:54 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E4389C0613CF; Sun, 29 Nov 2020 04:26:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=3+rYoc55tiwS75r5UCguG8RQp9uhLP5n17rDjyfEd7Y=; b=tLLVBytJxX+unnNEkq5U+SIOYx D4HQ1CXpb70Mxz8rmgaygXLoT0KibBXJymI6seriwwVWnh/2ChpV1RtHW6b1QBcBt5T8/Qxlqghzs diinud7/xixia1gJpwtMyIJkL1B9hxeggd+BARYKh+RSqldsepas95dZbi2zBvin+MLTaXrTTiPvM MZ9pAfDG9iN8EYHr0Lh3wfm7B2s7uEPZjRxaw0KnT+ENxu5IbsDl4+XhYRGBaWrcnIJVaWldnYFdg e46aNbywYl5kNGnRGs34OTfqQbDkn+FP0F7bpOe24kSr8kpXcRsSGQn2xbLMmWu0IHKwFBc2Idg0K BtVVVOyg==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kjLmC-0000Dl-Da; Sun, 29 Nov 2020 12:26:00 +0000 Date: Sun, 29 Nov 2020 12:26:00 +0000 From: Matthew Wilcox To: Hillf Danton Cc: syzbot , axboe@kernel.dk, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: KASAN: use-after-free Read in idr_for_each (2) Message-ID: <20201129122600.GA4327@casper.infradead.org> References: <000000000000ca835605b0e8a723@google.com> <20201129113429.13660-1-hdanton@sina.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201129113429.13660-1-hdanton@sina.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Nov 29, 2020 at 07:34:29PM +0800, Hillf Danton wrote: > > radix_tree_next_slot include/linux/radix-tree.h:422 [inline] > > idr_for_each+0x206/0x220 lib/idr.c:202 > > io_destroy_buffers fs/io_uring.c:8275 [inline] > > Matthew, can you shed any light on the link between the use of idr > routines and the UAF reported? I presume it's some misuse of IDR by io_uring. I'd rather io_uring didn't use the IDR at all. This compiles; I promise no more than that. diff --git a/fs/io_uring.c b/fs/io_uring.c index ef3cd7fe4416..2fcf196bb3c3 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -344,7 +344,7 @@ struct io_ring_ctx { struct socket *ring_sock; #endif - struct idr io_buffer_idr; + struct xarray io_buffers; struct idr personality_idr; @@ -1298,7 +1298,7 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p) INIT_LIST_HEAD(&ctx->cq_overflow_list); init_completion(&ctx->ref_comp); init_completion(&ctx->sq_thread_comp); - idr_init(&ctx->io_buffer_idr); + xa_init(&ctx->io_buffers); idr_init(&ctx->personality_idr); mutex_init(&ctx->uring_lock); init_waitqueue_head(&ctx->wait); @@ -3042,7 +3042,7 @@ static struct io_buffer *io_buffer_select(struct io_kiocb *req, size_t *len, lockdep_assert_held(&req->ctx->uring_lock); - head = idr_find(&req->ctx->io_buffer_idr, bgid); + head = xa_load(&req->ctx->io_buffers, bgid); if (head) { if (!list_empty(&head->list)) { kbuf = list_last_entry(&head->list, struct io_buffer, @@ -3050,7 +3050,7 @@ static struct io_buffer *io_buffer_select(struct io_kiocb *req, size_t *len, list_del(&kbuf->list); } else { kbuf = head; - idr_remove(&req->ctx->io_buffer_idr, bgid); + xa_erase(&req->ctx->io_buffers, bgid); } if (*len > kbuf->len) *len = kbuf->len; @@ -4130,7 +4130,8 @@ static int __io_remove_buffers(struct io_ring_ctx *ctx, struct io_buffer *buf, } i++; kfree(buf); - idr_remove(&ctx->io_buffer_idr, bgid); + if (nbufs != -1U) + xa_erase(&ctx->io_buffers, bgid); return i; } @@ -4148,7 +4149,7 @@ static int io_remove_buffers(struct io_kiocb *req, bool force_nonblock, lockdep_assert_held(&ctx->uring_lock); ret = -ENOENT; - head = idr_find(&ctx->io_buffer_idr, p->bgid); + head = xa_load(&ctx->io_buffers, p->bgid); if (head) ret = __io_remove_buffers(ctx, head, p->bgid, p->nbufs); @@ -4225,15 +4226,15 @@ static int io_provide_buffers(struct io_kiocb *req, bool force_nonblock, lockdep_assert_held(&ctx->uring_lock); - list = head = idr_find(&ctx->io_buffer_idr, p->bgid); + list = head = xa_load(&ctx->io_buffers, p->bgid); ret = io_add_buffers(p, &head); if (ret < 0) goto out; if (!list) { - ret = idr_alloc(&ctx->io_buffer_idr, head, p->bgid, p->bgid + 1, - GFP_KERNEL); + ret = xa_err(xa_store(&ctx->io_buffers, p->bgid, head, + GFP_KERNEL)); if (ret < 0) { __io_remove_buffers(ctx, head, p->bgid, -1U); goto out; @@ -8468,19 +8469,15 @@ static int io_eventfd_unregister(struct io_ring_ctx *ctx) return -ENXIO; } -static int __io_destroy_buffers(int id, void *p, void *data) -{ - struct io_ring_ctx *ctx = data; - struct io_buffer *buf = p; - - __io_remove_buffers(ctx, buf, id, -1U); - return 0; -} - static void io_destroy_buffers(struct io_ring_ctx *ctx) { - idr_for_each(&ctx->io_buffer_idr, __io_destroy_buffers, ctx); - idr_destroy(&ctx->io_buffer_idr); + unsigned long pgid; + struct io_buffer *buf; + + xa_for_each(&ctx->io_buffers, pgid, buf) { + xa_erase(&ctx->io_buffers, pgid); + __io_remove_buffers(ctx, buf, pgid, -1U); + } } static void io_ring_ctx_free(struct io_ring_ctx *ctx)